Surgical Correction of Ametropia with AddOn™ Intraocular Lens in Post-Penetrating Keratoplasty Pseudophakia

Abstract

Cataract surgery is the most common surgery in ophthalmology. The aim of cataract surgery is to restore vision in eyes in which the natural lens became opacified mostly due to the aging of the lens, or the presence of other ocular diseases, which promote earlier cataract formation. During cataract surgery, artificial intraocular lens (IOL) is implanted into the lens capsule and the value of the IOL is planned before surgery based on the preoperative IOL calculation. However, in the significant number of patients, cataract surgery may end up with a postoperative refractive error in which case patients have to wear glasses to reach the full vision for both distance and near correction (if monofocal IOL is used during cataract surgery!). Modern cataract surgery becomes more and more a refractive procedure as well, especially when multifocal and/or toric IOLs are implanted. However, in some specific cases where such IOLs are not applicable, high postoperative refractive error after cataract surgery can significantly influence the quality of the obtained vision. One such example is cataract surgery after penetrating keratoplasty. In this chapter, results of a novel approach of post-PK ametropia correction, namely implantation of sulcus placed AddOn IOLs (also called a piggyback lens) will be presented.

1. Introduction

In patients who have had penetrating keratoplasty (PK) cataract surgery cannot end up in emmetropia due to the fact that they all have significant postoperative astigmatism due to the presence of corneal graft. In eyes without corneal graft, which have significant astigmatism, the problem can be solved with the implantation of monofocal toric IOL, which can correct higher amounts of astigmatism. However, in patients with corneal graft, it is questionable whether to use monofocal toric IOL since we never know whether corneal graft will survive throughout patient life, or the graft will need to be changed later during patients’ life. If the graft needs to be changed and we have already implanted toric IOL during cataract surgery adjusted to the refractive error of the first corneal graft, the patient would have non-appropriate toric IOL in the eye. Thus, for patients with corneal graft, which develop cataract, we need a “reversible” correction of pre-existing astigmatism and, for that purpose, piggyback or AddOn IOLs are almost ideal option. Namely, AddOn IOLs can be easily and safely implanted in the ciliary sulcus over the already existing “in-the-bag” monofocal IOL, and if needed, they can be safely removed later on [1]. Thus, our method of choice for ametropia correction in post-PK patients who cannot wear contact lenses or spectacles to solve their ametropia is the implantation of AddOn IOL in the ciliary sulcus. This type of lens is used in eyes that already have had cataract surgery with implantation of conventional monofocal IOL in-the-bag. In this chapter, all the main aspects of add-on IOL usage in such cases are clarified.

2. Characteristics of 1stQ AddOn lens

The 1stQ AddOn is a single-piece hydrophilic monofocal IOL for implantation into the ciliary sulcus in addition to a primary IOL in the patient’s pseudophakic eye (Medicontur). This lens is implanted into the ciliary sulcus in addition to the IOL in the capsular bag and it is compatible with common capsular bag IOL, irrespective of design or material (Figure 1). Due to the lens convex-concave design, a space between AddOn IOL and posterior chamber IOL is approximately 0.5 mm, so there is no touch between the optics of the two implanted lenses. 1stQ AddOn lens is appropriate for the correction of both spherical refractive errors and astigmatism [1, 2]. The AddOn power calculation is typically made with the help of 1stQ AddOn®Calculator for the calculation of sulcus-fixated AddOn® IOLs. However, due to the fact that the amount of astigmatism is unusually “high” after PK, the calculation of the lens power for our specific cases was made by the manufacturer (Medicontur) and not by the operating surgeon. In post-penetrating keratoplasty cases, it was always implanted in the pseudophakic eye, although this type of lens can also be implanted in a single procedure namely together with the extraction of cataract (for example if the lens is used to correct presbyopia!). This type of IOL is very safe to implant into the sulcus due to the four important features: the lens has four flexible haptics, very good rotational stability due to its non-torque design, it is of convex-concave optic design enabling no IOL touch of adjacent eye structures, and it has square design making it safe regarding touch of the iris (“no iris capture” design) (Figure 2). The lens can be positioned safely irrespective of the size and shape of the ciliary sulcus [1, 2, 3].

Figure 1.

Position of 1stQ Addon lens in the ciliary sulcus (www.medicontur.com).

Figure 2.

main characteristics of 1stQ Addon lens (www.medicontur.com).

3. Surgical procedure

Implantation of AddOn IOL was always performed under topical anesthesia. The anterior chamber was filled with dispersive (on the corneal endothelium!) and cohesive viscoelastic after side-ports were formed. The incision size was 2.4–2.7 mm. The lens was loaded into the lens injector with viscoelastic and the tip of the injector was placed intracamerally prior to the insertion of AddOn IOL. The lens was injected very slowly in order to allow the leading haptic to unfold in a controlled manner and then the haptic was guided under the iris (Figure 3) [1]. During the injection procedure, care was taken not to push against the primary lens to maintain zonular stability. Due to its design, toric versions of the lens are easier to rotate into position without all four haptics positioned in the sulcus; thus, the lens was rotated into its desired position before placement of the other two haptics behind the iris. The lens could be rotated in either direction. Once the desired position of the toric lens was obtained, the other 2 haptics were also gently placed into the sulcus behind the iris, and a careful check-up was made to be sure that all four haptics are positioned behind the iris. It was very important to check that all four haptics are positioned behind the iris before removing the viscoelastic, particularly in our patients with corneal transplants, as it may be difficult to see the haptics behind the corneal scar. Some pearls for insertion include the use of the microscope with an integrated OCT image; thus, the surgeon can visualize the sulcus and position of the AddOn lens in the sulcus intraoperatively with the highest precision. It is also important to have good pupil dilation, and careful manipulation with the lens since in post-PK eyes special attention is needed not to destroy any endothelial cells during lens implantation. The advantage of post-PK eyes was that all the eyes had a very deep anterior chamber with enough space for manipulation with the lens.

Figure 3.

Implantation of a 1stQ Addon lens with the Medicel Accuject 2.1 injector (www.medicontur.com).

4. Ametropia correction in post-PK eyes

We have used AddOn IOL in post-PK eyes with a significant refractive error that could not be corrected by contact lens or spectacle wear. All of our post-PK eyes in which AddOn lens was implanted gained significant improvement in their non-corrected distance visual acuity and the satisfaction rate was extremely high. Implantation of the AddOn lens had no influence on near visual acuity and low-contrast acuity. A typical example of a post-PK eye in which cataract was already removed and posterior chamber IOL implanted in the capsular bag is shown in Figure 4, together with its corneal topography (measured by Pentacam) showing significant post-PK astigmatism (Figure 5). For each post-PK eye an individual Addon lens is ordered and produced according to patients’ individual measurements (Figure 6a and b). Lens implantation is made according to the previously described surgical procedure. The position of the lens after the surgery can be precisely checked postoperatively on the OCT scan of the anterior eye chamber to control for a proper distance between AddOn lens and PCIOL (Figure 7). The results of the significant increase in visual acuity in our first 3 post-PK eyes implanted with Addon IOL are represented in Figure 8. A dramatic increase in visual acuity from preoperative non-corrected (VA sc preop) is represented. The preoperative best-corrected (VA cc preop) is a vision tested by an eye doctor in the office; however, none of the patients could in fact wear such a correction in a real-life situation since their eyes did not support correction with either contact lens or spectacles. Therefore, their vision of 5–15% prior to AddOn lens implantation increased to 80–100% vision after AddOn lens implantation. As expected, with such a dramatic change in vision all patients were extremely satisfied with the outcome of the surgery. Those results are comparable with other publications [3, 4, 5].

Figure 4.

Slit-lamp image of the eye in which penetrating keratoplasty and cataract surgery with posterior chamber IOL implantation was done.

Figure 5.

Corneal topography of a post-PK pseudophakic eye showing significant astigmatism which can be corrected with Addon lens implantation.

Figure 6.

(a, b) Individual patient data and the outcome measurements for the individually designed Addon provided by manufacturer.

Figure 7.

OCT image showing position of AddOn IOL and the already existing PCIOL with adequate distance between the two lenses.

Figure 8.

Change in visual acuity after AddOn lens implantation in 3 representative post-PK cases.

Since patients with AddOn IOL in fact have two lenses in the eye; and despite the fact that AddOn IOL is very gentle and thin, we checked whether intraocular pressure (IOP) is increased by implantation of such lens and according to our results AddOn lens did not change values of IOP in 6 postoperative months of patients’ follow-up (Figure 9). A typical sample of corneal endothelial cell count pre- and post- Addon IOL implantation is shown in Figure 10. Due to the very deep anterior chamber in all post-PK eyes, the surgery of Addon IOL implantation did not influence the regularity and count of corneal endothelial cells.

Figure 9.

Intraoperative pressure (IOP) values before and after Addon IOL implantation.

Figure 10.

Endothelial cell density count pre- (10a) and post- (10b) AddOn IOL implantation.

5. Discussion

Penetrating keratoplasty can be a life-changing procedure for those patients who suffer from significant vision loss due to a corneal disease involving all corneal layers. Despite the fact that the success of this procedure may be limited by some postoperative complications like graft rejection, postoperative rise in intraocular pressure, or cataract formation, most of the patients with a clear corneal graft are extremely satisfied with their improvement of vision. In some cases, however, despite of the fact that the corneal graft is perfectly clear and there have been no postoperative complications jeopardizing the quality of the grafted tissue, we may end up with very unsatisfied patients with very low uncorrected visual acuity equal to or even worse as compared to preoperative vision. This happens in eyes with a corneal graft having very high postoperative astigmatism which cannot be corrected with a contact lens. Most often such cases develop after suturing of the graft with interrupted sutures or with the unexpected change in astigmatism after suture removal. We must bear in mind that the astigmatism is not only the result of the suture placement, but also a result of the type of healing process in each particular eye, so it may be that the patient has good vision and a low amount of astigmatism for a several months after surgery and then, unfortunately, develops a high astigmatism. Similarly, at the time of suture removal, we cannot judge the amount of astigmatism which will remain after suture removal. Recently new types of contact lens such as scleral lens has been developed to help in cases with very high astigmatism, but still, some patients remain who are not able to wear such lenses and who are in fact without any solution to improve their vision after PK. With the invention of AddOn lenses, which were primarily designed to correct refractive errors after more often performed surgeries like cataract surgery, corneal surgeons could also start to use such lenses for their post-PK patients. AddOn lenses are produced in a personalized manner as previously said, and according to individual patient refractive error. However, due to the high amount of astigmatism in some of post-PK cases it may happen that the manufacturer does not have an option of producing a lens for full astigmatism correction. We have also had such patients which were consequently “under-corrected” regarding their astigmatism. However, even if the full amount of astigmatism is not corrected with the AddOn lens, those patients still gained significantly better postoperative vision and were perfectly happy with obtained vision. Moreover, since in many of post-PK cases we do not have a regular type of astigmatism, we were worried that the outcome may not be as good as if the regular astigmatism is corrected. This is easily visible in Figure 5, where the irregularity of the post-PK astigmatism is clearly visible. However, clinically, despite the irregularity of post-PK astigmatism the visual outcome was better than expected and the patient satisfaction rate was high. Therefore, the AddOn lenses are the best and truly speaking the only currently available option for post-PK cases with high astigmatism, being of regular type (which is in fact rarely seen) or of the irregular type. The drawback of AddOn lenses that we have noticed was that the lens is not produced for extremely high amounts of astigmatism (>10 dioptres) and such high astigmatism may be seen in post-PK patients. Thus, the production of AddOn lens able to correct even higher amounts of astigmatism would be an improvement in 1stQAddOn lens portfolio. All the operated eyes, as mentioned before, were pseudophakic. We do know from the literature that refractive errors in pseudophakic eyes can sometimes be corrected with the replacement of the existing IOL. However, in post-PK cases, this is not an option since we would need to replace the IOL with toric IOL. However, in post-PK cases, the graft may be replaced in the future and then the toric IOL in the eye would be certainly not appropriate since astigmatism after repeated PK cannot be the same. Since AddOn lenses are not in use for a longer period of time for post-PK cases we still cannot comment on the performance of those lenses in a longer follow-up and this remains to be studied in the future. Namely, a follow-up of 6 months (which we have presented in this chapter) on the effect of AddOn lenses on postoperative IOP and on the state of endothelial cells should be studied in a long run as well.

6. Conclusion

Implantation of AddOn IOL in pseudophakic eyes with post-PK refractive error is safe and easy procedure to significantly improve visual acuity in post-PK cases unable to wear contact lenses or spectacles (at least for the shorter follow-up). Also, there was no adverse effect or IOP rise, and one of the main advantages is its reversibility in case of the next transplantation.